Battery cell of excellent heat dissipation property and middle or large-sized battery module employed with the same

ABSTRACT

Disclosed herein is a battery cell constructed in a structure in which an electrode assembly of a cathode/separator/anode structure is mounted in a battery case formed of a laminate sheet including a resin layer and a metal layer while the electrode assembly is connected to electrode terminals extruding out of the battery case, wherein the battery cell is constructed in a structure to accelerate heat dissipation by the heat conduction through at least some of a sealing part of the battery case where the electrode terminals are not located.

TECHNICAL FIELD

The present invention relates to a battery cell of excellent heatdissipation property, and, more particularly, to a battery cellconstructed in a structure in which an electrode assembly of acathode/separator/anode structure is mounted in a battery case formed ofa laminate sheet including a resin layer and a metal layer while theelectrode assembly is connected to electrode terminals extruding out ofthe battery case, wherein the battery cell is constructed in a structureto accelerate heat dissipation by heat conduction through at least someof a sealing part of the battery case where the electrode terminals arenot located.

BACKGROUND ART

As mobile devices have been increasingly developed, and the demand ofsuch mobile devices has increased, the demand of battery cells has alsosharply increased. Among them is a lithium battery cell having highenergy density and operating voltage and excellent preservation andservice-life characteristics, which has been widely used as an energysource for various electronic products as well as for the mobiledevices.

Based on their external and internal structures, battery cells aregenerally classified into a cylindrical battery, a prismatic battery,and a pouch-shaped battery. Especially, the prismatic battery and thepouch-shaped battery, which can be stacked with high integration andhave a small width to length ratio, have attracted considerableattention.

Also, the battery cells have attracted considerable attention as anenergy source for electric vehicles and hybrid electric vehicles, whichhave been developed to solve problems, such as air pollution, caused byexisting gasoline and diesel vehicles using fossil fuel. As a result,kinds of applications using the battery cells are being increased owingto advantages of the battery cells, and hereafter the battery cells areexpected to be applied to more applications and products than now.

As kinds of applications and products, to which the battery cells areapplicable, are increased, kinds of batteries are also increased suchthat the batteries can provide powers and capacities corresponding tothe various applications and products. Furthermore, there is a strongneed to reduce the sizes and weights of the batteries applied to thecorresponding applications and products.

For example, small-sized mobile devices, such as mobile phones, personaldigital assistants (PDA), digital cameras, and laptop computers, use oneor several small-sized, light-weighted battery cells for each deviceaccording to the reduction in size and weight of the correspondingproducts. On the other hand, middle- or large-sized devices, such aselectric vehicles and hybrid electric vehicles, use a middle- orlarge-sized battery module (which may be referred to as a “batterypack”) having a plurality of battery cells electrically connected witheach other because high power and large capacity is necessary for themiddle- or large-sized devices. The size and weight of the batterymodule is directly related to the receiving space and power of thecorresponding middle- or large-sized device. For this reason,manufacturers are trying to manufacture small-sized, light-weightedbattery modules.

Meanwhile, as battery cells are connected to one another, while thebattery cells are stacked, to increase the capacities of batterymodules, the dissipation of heat from the battery cells becomes serious.Heat is generated from lithium battery cells during the charge anddischarge of the lithium battery cells. If the heat is not effectivelyremoved, the heat accumulates in the respective lithium battery cells,with the result that the deterioration of the lithium battery cells iscaused, and the safety of the lithium battery cells is greatly lowered.In particular, for a battery requiring high-speed charging anddischarging characteristics as in a power source for electric vehiclesand hybrid electric vehicles, a large amount of heat is generated fromthe battery at the time when the battery instantaneously provides highpower.

Also, a laminate type battery case of a pouch-shaped battery widely usedin the battery module is coated with a polymer material exhibiting lowheat conductivity, with the result that it is difficult to effectivelylower the overall temperature of the battery.

In connection with this matter, for example, Japanese Patent ApplicationPublication No. 2005-302502 discloses a case for supporting a batterycell including a battery element of which the outer surface is formed ofa laminate film and cathode and anode terminals for charge and dischargeconnected to the battery element, the cathode and anode terminalsextruding from the laminate film, wherein a plate member having aplurality of empty spaces constitutes an upper body of a frame, theplate member being connected to another plate member in the thicknessdirection thereof, the inner circumferential part of the upper body ofthe frame serves as a support part for supporting four points of thebattery element around the battery element, and the innercircumferential part of the upper body of the frame communicates withthe outer circumferential part of the upper body of the frame such thatthe empty spaces are connected to one another. However, theabove-mentioned technology has problems in that it is necessary tomanufacture a battery cell case in a complicated structure and mount thebattery cell case to a battery, which is troublesome, and, whenbatteries are stacked to manufacture a battery module, the thickness andvolume of the battery module are greatly increased.

Therefore, there is a high necessity for a technology that is capable offundamentally solving the above-mentioned problems.

DISCLOSURE OF INVENTION Technical Problem

Therefore, the present invention has been made to solve the aboveproblems, and other technical problems that have yet to be resolved.

As a result of a variety of extensive and intensive studies andexperiments on a cutting frame, the inventors of the present inventionhave developed a battery cell constructed in a structure to accelerateheat dissipation by the heat conduction through at least some of asealing part of a battery case where no electrode terminals are located,and found that it is possible to effectively improve heat dissipationefficiency while not increasing the thickness of the battery cell. Thepresent invention has been completed based on these findings.

Technical Solution

In accordance with one aspect of the present invention, the above andother objects can be accomplished by the provision of a battery cellconstructed in a structure in which an electrode assembly of acathode/separator/anode structure is mounted in a battery case formed ofa laminate sheet including a resin layer and a metal layer while theelectrode assembly is connected to electrode terminals extruding out ofthe battery case, wherein the battery cell is constructed in a structureto accelerate heat dissipation by the heat conduction through at leastsome of a sealing part of the battery case where the electrode terminalsare not located.

That is, the battery cell according to the present invention isconstructed in a structure to accelerate heat dissipation through thesealing part of the battery case where no electrode terminals arelocated, whereby it is possible to easily discharge heat generatedduring the charge and discharge of the battery cell to the outside, andtherefore, it is possible to maximize the heat dissipation efficiency ofthe battery cell.

In a preferred embodiment, the heat dissipation accelerating structurethrough the sealing part is a structure in which at least some of thesealing part extends such that the at least some of the sealing part islonger than the remaining sealing part or a structure in which athermally conductive member is coupled to the sealing part.

In the structure having the extending sealing part or in the structurein which the thermally conductive member is coupled to the sealing part,as described above, heat generated from the battery cell due to ionocclusion/deocclusion reaction between a cathode active material and ananode active material during the charge and discharge of the batterycell is absorbed by the extending sealing part or the thermallyconductive member coupled to the sealing part, and then the absorbedheat is effectively discharged out of the battery cell.

The battery cell as described above is more preferably used in thestructure of a battery module including a plurality of battery cellsstacked. That is, when the battery cells are stacked in a structure inwhich the battery cells are in tight contact with each other, or in astructure in which the battery cells are adjacent to each other, toconstruct a battery module, it is difficult to dissipate heat generatedfrom the battery cells to the outside due to the structure in which thebattery cells are close to each other. Even in the stacked structure,however, the sealing parts of the respective battery cells are not closeto each other. According to the present invention, it is possible toeffectively dissipate the heat generated from the battery cells to theoutside through the sealing parts of the respective battery cells.

Also, the structure having the extending sealing part or the structurein which the thermally conductive member is coupled to the sealing partexhibit a high heat dissipation property while not reducing theproductivity of the battery cells due to the simple structuralcharacteristics thereof.

According to the present invention, the battery cell is not particularlyrestricted so long as the battery cell is a secondary battery that canbe charged and discharged. For example, a lithium secondary battery, anickel-metal hydride (Ni-MH) secondary battery, or a nickel-cadmium(Ni—Cd) secondary battery may be used as the battery cell. Preferably,the lithium secondary battery is used as the battery cell, since thelithium secondary battery provides a high power to weight ratio.

Based on its shape, the lithium secondary battery may be classified as acylindrical battery, a prismatic battery, or a pouch-shaped battery. Thebattery cell according to the present invention is applied to a batteryhaving a sealing part thermally welded at an outer circumference endregion thereof. In a preferred embodiment, the battery cell according tothe present invention is a light-weighted pouch-shaped batteryconstructed in a structure in which an electrode assembly is mounted ina battery case formed of a laminate sheet including an inner resinlayer, which is thermally weldable, an isolation metal layer, and anouter resin layer exhibiting excellent durability.

It is preferred to appropriately adjust the size of the extendingsealing part within a range in which the heat dissipation efficiency ofthe battery cell is maximized while the total volume of the battery cellis not increased. For example, therefore, the extending sealing part mayhave an extension length equivalent to 150 to 400% of the width of theremaining sealing part.

Also, the extending sealing part may be equivalent to more than 50%,preferably more than 70%, of the length of the sealing part of thebattery cell where the extending sealing part is formed. The extendingsealing part may extend in a single continuous structure or in two ormore discontinuous structures in the longitudinal direction of thesealing part.

The thermally conductive member may be coupled to a general sealing partor the above-described extending sealing part. The latter couplingstructure is more preferred.

In a preferred embodiment, at least some of the thermally conductivemember is joined to the outer surface of the sealing part.

In this structure, for example, the thermally conductive member may beformed of a plate-shaped member having a size greater than the width ofthe sealing part. When the width of the thermally conductive member isgreater than the width of the sealing part, it is possible to exhibit ahigh heat dissipation property due to the large heat dissipation surfacearea.

The thermally conductive member may be coupled to the sealing part invarious fashions. For example, the thermally conductive member may becoupled to the sealing part in a mechanical coupling fashion, in anadhesive fashion, or in a thermal welding fashion.

When the thermally conductive member is coupled to the sealing part inthe adhesive fashion, an adhesive may be applied to one major surface ofthe thermally conductive member or the sealing part corresponding to theone major surface of the thermally conductive member, and then thethermally conductive member is pressed against the sealing part suchthat the thermally conductive member is attached to the sealing part. Inthis case, any general bonding agents may be used as the adhesive.According to circumstances, an additive to increase heat conductivitymay be added to the adhesive.

When the thermally conductive member is coupled to the sealing part inthe thermal welding fashion, the thermally conductive member, which is athin plate-shaped member, is coupled to the outer surface of the sealingpart by thermal welding. This coupling structure hardly increases theoverall thickness of the battery cell, and therefore, this couplingstructure is particularly preferred when manufacturing a compact batterymodule by stacking a plurality of battery cells.

In another preferred embodiment, the thermally conductive member is aplate-shaped member having a size greater than the width of the sealingpart, and at least some of the thermally conductive member is thermallywelded to the laminate sheet while being interposed between upper andlower parts of the laminate sheet.

Generally, the battery cell is manufactured by placing an electrodeassembly in a battery case formed of a laminate sheet and thermallywelding the outer circumference of the battery case. Before thermallywelding the battery case, the thermally conductive member is interposedbetween the upper laminate sheet and the lower laminate sheet at theouter circumference of the battery case where no electrode terminals arelocated, and then the thermal welding is carried out such that thethermally conductive member is coupled to the upper laminate sheet andthe lower laminate sheet. As a result, it is possible to easilymanufacture the battery cell having the thermally conductive membercoupled thereto without an additional process. By this couplingstructure, therefore, it is possible to more stably couple the thermallyconductive member to the battery case while not complicating the batterymanufacturing process.

Meanwhile, the thermally conductive member may be appropriately modifiedinto a structure to increase heat dissipation efficiency and coupling tothe sealing part. Preferably, the thermally conductive member has anouter circumferential end thermally welded to the sealing part, and theouter circumferential end of the thermally conductive member isconstructed in a concavo-convex structure on a horizontal plane, therebyincreasing a coupling force between the thermally conductive member andthe laminate sheet while securing a large thermally welded area betweenthe upper and lower parts of the laminate sheet.

The concavo-convex structure formed at the outer circumferential end ofthe thermally conductive member is not particularly restricted so longas the concavo-convex structure can increase a coupling force betweenthe thermally conductive member and the sealing part. For example, theconcavo-convex structure may be a saw-toothed concavo-convex structureor a wave-shaped concavo-convex structure.

In another example, the thermally conductive member may have an outercircumferential end thermally welded to the sealing part, and the outercircumferential end of the thermally conductive member may beconstructed in a concavo-convex structure on a vertical sectional plane,thereby increasing a coupling force between the thermally conductivemember and the laminate sheet.

The concavo-convex structure on the horizontal plane or theconcavo-convex structure on the vertical sectional plane increases acoupling force between the thermally conductive member and the sealingpart, and, in addition, greatly increases the contact interface betweenthe thermally conductive member and the sealing part. Consequently, itis possible to further improve the heat dissipation efficiency of thebattery.

According to circumstances, the thermally conductive member may have anouter circumferential end thermally welded to the sealing part, and oneor more through-holes may be formed in the outer circumferential end ofthe thermally conductive member such that the upper and lower parts ofthe laminate sheet are partially thermally welded to each other via thethrough-holes.

The thermally conductive member is not particularly restricted so longas the thermally conductive member is made of a material exhibitingexcellent heat conductivity and is formed in a thin shape. Preferably,the thermally conductive member is formed of a metal or carbon plate,which exhibits heat conductivity higher than other materials, or apolymer sheet containing metal powder or carbon powder, which exhibitsheat conductivity higher than other materials.

When the thickness of the thermally conductive member is too large, thevolume and weight of a battery module may increase during the stackingof the battery cells to manufacture the battery module. On the otherhand, when the thickness of the thermally conductive member is toosmall, it is difficult to expect a desired heat dissipation effect, andit is difficult to handle the thermally conductive member. For example,therefore, the thickness of the thermally conductive member may be equalto or greater than the thickness of the laminate sheet.

Meanwhile, a plurality of battery cells are stacked to construct amiddle- or large-sized battery module such that the middle- orlarge-sized battery module provides high power and large capacity. Thebattery cells, used as unit cells of the battery module, are required toexhibit high heat dissipation efficiency, which is necessary to securethe safety of the battery module, as well as operational properties.

Therefore, the thermally conductive member may be constructed in astructure to contact a heat exchange medium. For example, the structureto contact the heat exchange medium may be a structure in which a heatexchange member having a channel through which the heat exchange medium(for example, a coolant) flows is in contact with the thermallyconductive member.

That is, the heat exchange member is in contact with a specific regionof the thermally conductive member excluding the end of the heatexchange member coupled to the sealing part, and therefore, it ispossible to further accelerate the heat dissipation of the battery cellwhile not increasing the thickness of the battery cell.

Preferably, the thermally conductive member is bent to partially wrapthe heat exchange member at the end of the thermally conductive memberopposite to a region of the thermally conductive member coupled to thesealing part.

Since the thermally conductive member is bent to partially wrap the heatexchange member at the end of the thermally conductive member oppositeto a region of the thermally conductive member coupled to the sealingpart, the heat dissipation of the battery cell through the thermallyconductive member and the heat exchange member is further easilyachieved. Consequently, the above-described structure is moreeffectively applicable to a middle- or large-sized battery modulemanufactured by stacking a plurality of battery cells.

In accordance with another aspect of the present invention, there isprovided a middle- or large-sized battery module having a high power andlarge capacity, wherein the battery module includes the above-describedbattery cell as a unit cell.

The middle- or large-sized battery module may be used as a power sourcefor devices which require high-power and large-capacity electricity andto which external forces, such as vibration and impact, are applied.Preferably, the middle- or large-sized battery module is used as a powersource for electric vehicles or hybrid electric vehicles.

The structure of the middle- or large-sized battery module and a methodof manufacturing the middle- or large-sized battery module are wellknown in the art to which the present invention pertains, and therefore,a detailed description thereof will not be given.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a plan view typically illustrating a battery cell according toa preferred embodiment of the present invention;

FIG. 2 is a plan view typically illustrating a coupling region between athermally conductive member and a sealing part of a battery caseaccording to another preferred embodiment of the present invention;

FIGS. 3 to 5 are vertical sectional views typically illustratingcoupling regions between the thermally conductive member and the sealingpart of the battery case according to other preferred embodiments of thepresent invention;

FIG. 6 typically illustrates various structures of a battery cellaccording to various preferred embodiments of the present invention; and

FIG. 7 is a perspective view illustrating a battery cell constructed ina structure in which a heat exchange member is further coupled to thebattery cell of FIG. 1.

MODE FOR THE INVENTION

-   -   Now, preferred embodiments of the present invention will be        described in detail with reference to the accompanying drawings.        It should be noted, however, that the scope of the present        invention is not limited by the illustrated embodiments.

FIG. 1 is a plan view typically illustrating a battery cell according toa preferred embodiment of the present invention.

Referring to FIG. 1, the battery cell 100 includes an electrode assembly120 of a cathode/separator/anode structure, mounted in a battery case130 formed of a laminate sheet, electrode terminals 140 and 142extruding out of the battery case 130, and a thermally conductive member150 coupled to a sealing part 110 of the battery case 130 where theelectrode terminals 140 and 142 are not located.

The thermally conductive member 150 has a width W greater than the widthw of the sealing part 110, with the result that it is possible to securea large heat dissipation surface area. Consequently, heat generatedduring the charge and discharge of the electrode assembly 120 isdischarged to the outside through the sealing part 110 and the thermallyconductive member 150, which is formed in the shape of a plate.

FIG. 2 is a plan view typically illustrating a coupling region between athermally conductive member and a sealing part of a battery caseaccording to another preferred embodiment of the present invention.

Referring to FIG. 2, the coupling region between the sealing part 110 ofthe battery case and the thermally conductive member 150 is constructedin a saw-toothed concavo-convex structure 152 on a horizontal plane.Consequently, when the thermally conductive member 150 is insertedbetween upper and lower laminate sheets (not shown) of the battery caseand then is welded to the upper and lower laminate sheets, contactinterfaces 151 between the upper and lower laminate sheets and betweenthe thermally conductive member 150 and the respective laminate sheets,and therefore, it is possible to increase a coupling force between thethermally conductive member 150 and the laminate sheets while securing alarge thermally welded area between respective laminate sheets.

FIGS. 3 to 5 are vertical sectional views typically illustratingcoupling regions between the thermally conductive member and the sealingpart of the battery case according to other preferred embodiments of thepresent invention.

Referring first to FIG. 3, an end 154 of the thermally conductive member150 is thermally welded to an upper laminate sheet 112 and a lowerlaminate sheet 114 of the sealing part of the battery case while the end154 of the thermally conductive member 150 is interposed between theupper laminate sheet 112 and the lower laminate sheet 114.

Referring to FIG. 4, the end 154 of the thermally conductive member 150is constructed in a concavo-convex structure 156 on a vertical sectionalplane. Consequently, when the end 154 of the thermally conductive member150 is welded to the upper laminate sheet 112 and the lower laminatesheet 114, it is possible to provide a high coupling force between thethermally conductive member and the laminate sheets due to the largecoupling interfaces.

Referring to FIG. 5, one or more through-holes 158 are formed in the end154 of the thermally conductive member 150. Consequently, some of theupper laminate sheet 112 and some of the lower laminate sheet 114 aredirectly thermally welded to each other via the through-holes 158,thereby further increasing a coupling force between the thermallyconductive member and the laminate sheets.

FIG. 6 typically illustrates various structures of a battery cellaccording to various preferred embodiments of the present invention.

Referring to FIG. 6, a sealing part 210 of the battery cell 200 where anelectrode terminal 240 is not located may be constructed in threedifferent structures to accelerate heat dissipation.

In the first structure, one side sealing part 211 extends such that theone side sealing part 211 is longer than the other side sealing part216. In the second structure, a thermally conductive member 220 iscoupled to the bottom of the sealing part 210. In the third structure,an end of the thermally conductive member 220 is thermally welded to anupper laminate sheet 212 and a lower laminate sheet 214 of the sealingpart 210 while the end of the thermally conductive member 220 isinterposed between the upper laminate sheet 212 and the lower laminatesheet 214.

FIG. 7 is a perspective view illustrating a battery cell constructed ina structure in which a heat exchange member is further coupled to thebattery cell of FIG. 1.

Referring to FIG. 7, the plate-shaped thermally conductive member 150 iscoupled to a specific region of the sealing part 110 of the battery cell300. An end of the thermally conductive member 150 is bent to partiallywrap the heat exchange member 310 having a channel 312 through which acoolant flows. In this structure, therefore, it is possible to furtheraccelerate the dissipation of heat from the battery cell 300 while notincreasing the thickness of the battery cell 300. Consequently, thebattery cell of this structure is effectively applicable to a middle- orlarge-sized battery module (not shown).

INDUSTRIAL APPLICABILITY

As apparent from the above description, the battery cell according tothe present invention is constructed in a structure to accelerate heatdissipation by the heat conduction through at least some of the sealingpart of the battery case where no electrode terminals are located.Consequently, it is possible to effectively improve heat dissipationefficiency while not increasing the thickness of the battery cell.

Furthermore, it is possible to manufacture a battery cell of which theheat dissipation efficiency is improved in a simple structure. In thiscase, it is possible to uniformly control the internal temperature ofthe battery cell. Consequently, it is possible to greatly improve thelife span and safety of the battery cell.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

1. A battery cell constructed in a structure in which an electrodeassembly of a cathode/separator/anode structure is mounted in a batterycase formed of a laminate sheet including a resin layer and a metallayer while the electrode assembly is connected to electrode terminalsextruding out of the battery case, wherein the battery cell isconstructed in a structure to accelerate heat dissipation by the heatconduction through at least some of a sealing part of the battery casewhere the electrode terminals are not located.
 2. The battery cellaccording to claim 1, wherein the heat dissipation acceleratingstructure through the sealing part is a structure in which at least someof the sealing part extends such that the at least some of the sealingpart is longer than the remaining sealing part or a structure in which athermally conductive member is coupled to the sealing part.
 3. Thebattery cell according to claim 1, wherein the laminate sheet includesan inner resin layer, which is thermally weldable, an isolation metallayer, and an outer resin layer exhibiting excellent durability.
 4. Thebattery cell according to claim 2, wherein at least some of thethermally conductive member is joined to the sealing part.
 5. Thebattery cell according to claim 2, wherein the thermally conductivemember is a plate-shaped member having a size greater than the width ofthe sealing part, and at least some of the thermally conductive memberis thermally welded to the laminate sheet while being interposed betweenupper and lower parts of the laminate sheet.
 6. The battery cellaccording to claim 5, wherein the thermally conductive member has anouter circumferential end thermally welded to the sealing part, and theouter circumferential end of the thermally conductive member isconstructed in a concavo-convex structure on a horizontal plane, therebyincreasing a coupling force between the thermally conductive member andthe laminate sheet while securing a large thermally welded area betweenthe upper and lower parts of the laminate sheet.
 7. The battery cellaccording to claim 5, wherein the thermally conductive member has anouter circumferential end thermally welded to the sealing part, and theouter circumferential end of the thermally conductive member isconstructed in a concavo-convex structure on a vertical sectional plane,thereby increasing a coupling force between the thermally conductivemember and the laminate sheet.
 8. The battery cell according to claim 5,wherein the thermally conductive member has an outer circumferential endthermally welded to the sealing part, and one or more through-holes areformed in the outer circumferential end of the thermally conductivemember such that the upper and lower parts of the laminate sheet arepartially thermally welded to each other via the through-holes.
 9. Thebattery cell according to claim 2, wherein the thermally conductivemember is formed of a metal or carbon plate or a polymer sheetcontaining metal powder or carbon powder.
 10. The battery cell accordingto claim 2, wherein the thermally conductive member is constructed in astructure to contact a heat exchange medium.
 11. The battery cellaccording to claim 10, wherein the structure to contact the heatexchange medium is a structure in which a heat exchange member having achannel through which the heat exchange medium flows is in contact withthe thermally conductive member.
 12. The battery cell according to claim11, wherein the thermally conductive member is bent to partially wrapthe heat exchange member at the end of the thermally conductive memberopposite to a region of the thermally conductive member coupled to thesealing part.
 13. A middle- or large-sized battery module having a highpower and large capacity, wherein the battery module includes thebattery cell according to claim 1 as a unit cell.
 14. The middle- orlarge-sized battery module according to claim 13, wherein the batterymodule is used as a power source for electric vehicles or hybridelectric vehicles.